Rosai Dorfman disease: appearances can be deceptive.

A 14-year-old boy was referred to us with a history of progressive painless massive symmetrical cervical lymphadenopathy, provisionally diagnosed as lymphoma. Multiple biopsies were needed, and confirmed the diagnosis of Rosai Dorfman disease (RDD), which is a very rare benign condition. Sinus histiocytosis with massive lymphadenopathy, also known as RDD, manifests as bulky lymphadenopathy in children and young adults. Extranodal sites such as the skin, upper airways, gastrointestinal tract and central nervous system can be involved. There is a characteristic pattern of lymphoid proliferation with a thick fibrous capsule, distention of lymphoid sinuses, accumulation of plasma cells and proliferation of large, often atypical, histiocytes showing emperipolesis is characteristic. The disease is considered to be benign and usually self-limited. We emphasise the need for doing a repeat lymphnode biopsy even if the prior histopathology is suggestive of reactive lypmhnode hyperplasia in every case of persisting lymphadenopathy.